The RD400 drag bike

[sirch345]

In our defence we were running into a 20mph headwind which must have knocked a bit off the top speed

I would be more than happy with the times you and Tony achieved. I think you both did really well

I wonder if Tony has seen my data I found in my previous post yet

Chris.

Yes, I did, Chris. My storm was quite a bit lighter then, and so was I!

Very impressive stats I thought, do you realise Tony that was in 2008

Chris.

[AMCQ46]

Rebuild is started.

Phase 1 :
A) get the crank rebuilt with new rods, all new brgs, labyrinth seal, trued up then welded
B) get the barrels bored out to 2nd oversize,
C) cut windows in the back of the pistons to suit the boost port.

I would then collect these parts, rebuild the bottom end , put it in the frame, chain on, carbs on, ignition on etc and take the whole bike back for phase 2.

Phase 2:
A) reprofile the combustion chamber in the heads to suit the new piston curve
B) set the squish
C) cut up the expansion pipes and lengthen them by making them cross over, making all the shapes so they fit the frame and avoid the foot controls
D) get it started and time up the ignition and get some heat cycles on the engine.


Harry the engine tuner goes off to Thailand (for 3 months) in 4 weeks time, so I had the chase him to get my engine phase 1 work done, as I will only have 5 days available before he goes away to get phase 2 done.

He said he would have the bits done for me to collect Saturday, but the crankshaft fought him for 3 days as it is getting old and sloppy from being taken apart too often in the past. Getting it to run true took him till Friday night so when i arrived we still had to do the barrels and pistons.

While the boring was going on, we checked the crank on the bottom cases and noticed that the new main bearing had much bigger locating pegs and they were in a slightly different position too. So we had to cut new locations into the cases to suit, then wash it all again for assembly.

With the crank now in, I put the gear clusters back in, added gasket compound to the mating faces and bolted them together.

Once the bores were cut to the new size we dry fitted them with the piston (no rings) and new .5mm base gaskets to check the deck height and port timings on each side to see if they are matched.
Harry wasn’t happy with one exhaust port higher than the other and some variations in the transfers, so he scribed a line where he wanted them to be and got his porting tools out to cut them to the new height and shape.

Then he started the honeing process to get the piston clearance up to 0.0025” and a good surface finish for the rings to bed to.
This should have been easy but the large ports keep catching the edge of the stones and breaking them off the tool holder, so about 2 hr later we have the clearance right on both barrels!!!!!!!!!

It has taken us 9hrs to get to this point and we still haven’t cut the piston windows in! so that just puts a bit more work onto the phase 2 visit.

Some photos

This was the crank waiting for assy with its new rods

Crank bits ready

Then once assembled checking the runout

Crank true

The boring bit…… literally

The boring

Engine together to check the deck height (how much the piston is above or below the top of the barrel)

Deck height check

Deck height check

Adjusted the transfer ports

Fixing the porting

And I noticed some std rd400 barrels so it was interesting to see the difference

Std RD 1

Std RD2

And as he makes most of his money in scooters now, here is one of the street tuned Lambretta motors with special barrels and his billet head

Lambretta 225 special

[fabiostar]

2 stroke porn

[AMCQ46]

Back in the frame now

@Sirch345 …….. look….. more rubber bands on the back brake pedal,

[sirch345]

Rebuild is started.

Phase 1 :
A) get the crank rebuilt with new rods, all new brgs, labyrinth seal, trued up then welded
B) get the barrels bored out to 2nd oversize,
C) cut windows in the back of the pistons to suit the boost port.

I would then collect these parts, rebuild the bottom end , put it in the frame, chain on, carbs on, ignition on etc and take the whole bike back for phase 2.

Phase 2:
A) reprofile the combustion chamber in the heads to suit the new piston curve
B) set the squish
C) cut up the expansion pipes and lengthen them by making them cross over, making all the shapes so they fit the frame and avoid the foot controls
D) get it started and time up the ignition and get some heat cycles on the engine.


Harry the engine tuner goes off to Thailand (for 3 months) in 4 weeks time, so I had the chase him to get my engine phase 1 work done, as I will only have 5 days available before he goes away to get phase 2 done.

He said he would have the bits done for me to collect Saturday, but the crankshaft fought him for 3 days as it is getting old and sloppy from being taken apart too often in the past. Getting it to run true took him till Friday night so when i arrived we still had to do the barrels and pistons.

While the boring was going on, we checked the crank on the bottom cases and noticed that the new main bearing had much bigger locating pegs and they were in a slightly different position too. So we had to cut new locations into the cases to suit, then wash it all again for assembly.

With the crank now in, I put the gear clusters back in, added gasket compound to the mating faces and bolted them together.

Once the bores were cut to the new size we dry fitted them with the piston (no rings) and new .5mm base gaskets to check the deck height and port timings on each side to see if they are matched.
Harry wasn’t happy with one exhaust port higher than the other and some variations in the transfers, so he scribed a line where he wanted them to be and got his porting tools out to cut them to the new height and shape.

Then he started the honeing process to get the piston clearance up to 0.0025” and a good surface finish for the rings to bed to.
This should have been easy but the large ports keep catching the edge of the stones and breaking them off the tool holder, so about 2 hr later we have the clearance right on both barrels!!!!!!!!!

It has taken us 9hrs to get to this point and we still haven’t cut the piston windows in! so that just puts a bit more work onto the phase 2 visit.

Some photos

This was the crank waiting for assy with its new rods
IMG_0288.jpeg

Then once assembled checking the runout
IMG_5187.jpeg

The boring bit…… literally
IMG_5184.jpeg

Engine together to check the deck height (how much the piston is above or below the top of the barrel)
IMG_5193.jpegIMG_5193.jpeg

Adjusted the transfer ports
IMG_5195.jpeg

And I noticed some std rd400 barrels so it was interesting to see the difference
IMG_5188.jpeg
IMG_5196.jpeg


And as he makes most of his money in scooters now, here is one of the street tuned Lambretta motors with special barrels and his billet head
IMG_5186.jpeg

I read this late last evening. A cracking read Al, many thanks for updating this build, and for adding the photo's

Back in the frame now

IMG_5198.jpeg

IMG_5199.jpeg

@Sirch345 …….. look….. more rubber bands on the back brake pedal,

I hope you have taken out a Patent on this Al

Chris.

[Duffy1964]

Great write up Al and making great progress. Well done


Sent from my iPhone using Tapatalk

[AMCQ46]

back to Phase 2 of the build.

the number of days I had available to get the bike back up to Leicester dropped from 4 to 1 due to The plastic overmolded pulley on my vans power steering pump deciding to fail when I was heading up to Oulton Park to Marshall for the BSB weekend. When it failed it quickly ripped the drive belt which then took out the alternator drive and as it was dark and raining at the time, I only just made it the remaining 30miles to Oulton Park before the voltage dropped so low all the ECUs were throwing fault lamps and the electric windows wouldn't go back up.


long story short, I got the battery charged when I was at the race meeting and also hot wired the leisure battery to the vehicle battery so I now had double the Ah capacity so I would have 1hr of driving .... but not enough to get me the 160 miles home. found a garage up in Cheshire that would take the job on but not till the week after..... that worked for me as I was off to Sardinia for a week, so I left the van there and MrsMcQ came up to collect me.

once back from playing on the Ducati V2 in Sardinia I got the train up to the garage and with my van back I could now take the bike to Harrys tuning shop in Leicester on Tuesday 21st May, just 2 days before he goes back to Thailand and the day before I was heading to Bearded Theory festival.

Got to Harrys a bit later than planned a bad crash on the M69 stopped traffic for 40 mins,

Starting point

Arrived for rebuild

From there we started with modifying the pistons to put holes in the back to feed the boost port and also take some material off the bottom so they dont foul the crank.
Then just to be sure all was good he weighed the pistons and there was a 0.3g difference….WTF! That way to much!

Pistons

Looking at the pistons one has machining inside but the other doesn’t, but in Harry’s view that isn’t enough to make the difference …. He has a plan though, he has some other piston pins that are thinner walled steel, so he will use one of those in the heavy piston to match the combined weight. Even then he has to grind some more material from the pin bore to get it right.

Once that is done we put the barrels and pistons on and check the deck height again, there is a slight difference, so the RH side gets a 0.75mm base gasket and the LH gets a 0.5mm so that gets them both to zero deck (ie the pistons os flush with the top of the barrel at TDC). That means both heads can be cut the same and the squish is a combination of the way the head is cut and the 0.35mm head gasket.

Barrels on

So now Harry sets the heads in the lathe and profiles the squish shape and step, then scribes the details on the underside for future reference.

Heads

Then the heads go back on and while I clock TDC and set the ignition timing, Harry starts cutting up the previously butchered expansions pipes which are both too short and also have some dubious steps inside.

Heads on

Harry knows what what length we need and can see where they have been cut and shut so recuts there, he then works out what cone shape is needed to mate the 2 diameters and provide the required length. Once the tube is cut and rolled, we then can look at how it needs to be scalloped to mate the body of the pipe to the header and also put the pipes out wide to the side so the bike can be lowered much more.

Pipe 1

Much cutting and welding later and the pipes are in place and rubber mounted off the engine casings rather than the frame rails.

Welding pipes

Pipes fitted side view

It’s now 10.30pm and it’s time to see if it starts………….yes it does

We did one heat cycle and at 11pm I put the bike back in the van and set off home, emptied the van of bike stuff and then loaded it with all the camper van stuff for 5 days at a music festival. Long but successful day.

[Pete.L]

Jeeze!
You're making retirement sound very hectic!
I think I'll keep working a bit longer.

Sounds like it's all coming together nicely. When are you planning to use it anger Ali?

Pete

[AMCQ46]

Jeeze!
You're making retirement sound very hectic!
I think I'll keep working a bit longer.

Sounds like it's all coming together nicely. When are you planning to use it anger Ali?

Pete

Not got anything booked, but after all this effort I will sort out an event at Melbourne raceway, although that is only 1/8th mile

[sirch345]

Another great read Al, thanks for posting up, and for the added photo's

I'm amazed you actually got the bike all back together and fired up in the time you had, things were certainly against you.
Lucky you had Harry willing to work so late too

You must have been elated when at last the engine first fired up,

Chris.

[neil]

Jeeze!
You're making retirement sound very hectic!
I think I'll keep working a bit longer.

Sounds like it's all coming together nicely. When are you planning to use it anger Ali?

Pete

Not got anything booked, but after all this effort I will sort out an event at Melbourne raceway, although that is only 1/8th mile

Elvington Top speed days have longer distances if that's what you want Al?

[Duffy1964]

Wow it’s getting some serious love, great work Al


Sent from my iPhone using Tapatalk

[AMCQ46]

Jeeze!
You're making retirement sound very hectic!
I think I'll keep working a bit longer.

Sounds like it's all coming together nicely. When are you planning to use it anger Ali?

Pete

Not got anything booked, but after all this effort I will sort out an event at Melbourne raceway, although that is only 1/8th mile

Elvington Top speed days have longer distances if that's what you want Al?

That’s good to know, how long are the runs there?

Until i am nappyy that the jetting with the new set up is good I think the 1/8th mile is a good starting point

[neil]

Its a 2 mile runway, timings get set up for different lengths at each meeting. I think longest is over a mle so better than Melbourne until they raise enough funds for extension. Let me know if you're going I'll try to go.

[MK_WF]

I hope you were kidding on the 0.3 g difference.

I even ran 0.5 mm different size and brand pistons like Prox & Wiseco as a quick and dirty weekend repair on my YPVS. That makes up for maybe something like 10 g.
Guess what: it didn't vibrate more, just in slightly other rpm ranges. That was all.

Compensating deck height with different base gaskets is possible, but not smart for long term use. Imagine next rebuild in 5 years - will you remember which thickness goes where?
Better put on the list to machine both cylinders to the same height in order to have everything symmetrical.